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Drinking Water: Private Wells

About 30 percent of Wisconsin residents get their drinking water from private wells.

What is a private well?

A well for drinking water.

A private well is a way to access groundwater. A well is “private” if it has fewer than 15 connections and serves fewer than 25 people.

A single person or an entity can own a private well. Examples include a small business, mobile home, or school.

Unlike public water systems, the owner of a private well is in charge of protecting and maintaining the well.

How do I maintain my well?

A private well needs regular maintenance and inspection. You want to make sure it’s working correctly. Here are ways to protect your well:

  • Avoid damaging the well casing. See Learn About Private Water Wells for a diagram of the parts of a well.
  • Keep the area around the well clean and safe.
  • Make sure the ground slopes away from the well.
  • Make sure your well cap is secure and in good condition. It shouldn’t have cracks, holes, or other damage.
  • Work with licensed professionals and keep records of all well work and testing. For a list of professionals, see Well and Heat Exchange Contractors.

What substances could be in my well water?

While most private wells in Wisconsin provide safe drinking water, some may contain substances that can affect our health. Many of these substances do not affect the color, smell, or taste of the water. The only way to make sure a well is safe for drinking is to test your well regularly using a Wisconsin certified lab.

These substances may be found in a private well in Wisconsin:

Arsenic is a mineral found in soil, bedrock, and water. Exposure to high levels of arsenic can impact our health.

It is important to test for arsenic regularly.

  • Test for arsenic at least once every five years.
  • Test once a year if arsenic was present in previous tests or you live in Outagamie, Winnebago, or Brown counties.

Our arsenic page has information on how to interpret your test results and what to do if arsenic levels are high and our Arsenic in Private Well Water Fact Sheet, P-45012 has this information in a printable format.

Atrazine is a weed killer that has been used on crops in Wisconsin for many years. High levels of atrazine may increase the risk of cancer and affect the nervous system, heart, and liver.

Private well users should test for atrazine if they live near agricultural fields or areas where pesticides are made, stored, or mixed. You can complete a screening test from the Wisconsin State Lab of Hygiene or the University of Wisconsin –Stevens Point.

Our atrazine page has information on how to interpret your test results and what to do if atrazine levels are high and our Atrazine in Private Well Water Fact Sheet, P-03500 has this information in a printable format.

Bacteria can get into wells when work is done on them, if the well was not built properly, or if there are nearby sources of animal or human waste. Bacteria can also get into water from flooding and manure spills.

Bacteria testing looks for signs that the water can make people sick.

  • Test for bacteria at least once a year.
  • Test right away if you notice a change in the color, taste, or smell of the water.

Our bacteria page has information on how to interpret your test results and what to do if bacteria are present and our Bacteria in Private Well Water Fact Sheet, P-02132 has this information in a printable format.

Fluoride is a naturally occurring mineral that is found in rocks, soil, and water. Low levels of fluoride can prevent cavities and support the development of strong teeth. However, moderate levels of fluoride can change teeth’s appearance in young children and high levels can cause bones to became brittle and fragile.

Test for fluoride at least once. Also test before the water will be used by someone who is pregnant or young children.

Our fluoride page has information on how to interpret your test results and our Fluoride in Private Well Water Fact Sheet, P-03521 has this information in a printable format.

Pipes, faucets, and other plumbing components in a home can contain lead. There is no safe level of lead exposure. Lead can affect learning, mental health, and increase the risk of diseases later in life.

Testing for your well for lead helps you learn about your water quality.

  • Test for lead every five years.
  • Also test before the water will be used by someone who is or may become pregnant and by babies.

Our lead in water page has information on how you can protect yourself and your family from this hazard and our Lead in Drinking Water Fact Sheet, P-02602 has this information in a printable format.

Manganese is a common element found in minerals, rocks, and soil. While small amounts of manganese are part of a healthy diet, high levels can affect our health.

Test for manganese if your water is brown or black or stains your faucets, sinks, or laundry.

Our manganese page has information on how to interpret your test results and what to do if manganese levels are high and our Manganese in Private Well Water Fact Sheet, P-45103A has this information in a printable format.

Nitrate is a natural molecule found in plants and animals. When it gets in our drinking water, it can affect our health.

It is important to test nitrate regularly.

  • Test for nitrate at least once a year.
  • Test before the water will be used by someone who is or may become pregnant and babies.
  • Test right away if you notice a change in the color, taste, or smell of the water.

Our nitrate page has information on how to interpret your test results and what to do if nitrate levels are high and our Nitrate in Private Well Water Fact Sheet, P-02128 has this information in a printable format.

Per- and polyfluoroalkyl substances (PFAS) are a group of chemicals that have been used in many products for their heat, grease, and water-resistant properties. Exposure to high levels of some PFAS can affect our health.

if you live near a PFAS contamination site, connect with your local municipality and the DNR to learn potential testing resources. If you do not live near a site of environmental contamination, it is unlikely that PFAS are a problem in your drinking water.

Our PFAS webpage has information on how you can protect yourself and your family this contaminant. Our PFAS in Private Well Water Fact Sheet, P-03212 has this information in a printable format.

Strontium is a mineral that has radioactive and non-radioactive forms. Non-radioactive strontium is formed naturally and is commonly found in Wisconsin. Exposure to high levels of non-radioactive strontium in drinking water can affect how bones develop.

Test for strontium if you live in eastern or northern Wisconsin.

Test twice over a two-year period in two different seasons. It is best to test in the fall and spring.

Our strontium page has information on how to interpret your test results and what to do if nitrate levels are high and our Strontium in Private Well Water Fact Sheet, P-02434p has this information in a printable format.

TCE is a human-made chemical with many commercial and industrial uses including dry cleaning and grease removal. High levels of TCE can affect the kidneys, liver, lung, and immune system and may cause heart defects in unborn babies.

Test for TCE if you live within a quarter mile of a landfill, industrial site, gas station, or dry cleaner.

Our trichloroethylene page has information on how to interpret your test results and what to do if TCE levels are high.

What can I do if there are contaminants in my water?

Short-term options

  • If your water contains elevated levels of a contaminant, you should use a different source of water for drinking, making baby formula, and preparing foods that take up a lot of water (like oatmeal, rice and gelatin).
  • Options for different water include bottled water, water from a well without issues, and water from a public system.
  • Information on how to address specific contaminants can be accessed above or from our chemicals list.

Long-term options

  • One option is to drill a new well to access water that is not affected. Because this can be a complex process, it is best to work with your regional private well specialist.

    The Wisconsin Department of Natural Resource's well compensation grants provide funds to address public health hazards in private wells.

  • Another option is to install a certified treatment device. Using a certified device is important because it means the device has met a set of voluntary manufacturing and performance standards.

    Our Water Treatment Devices for Private Well Contaminants fact sheet, P-45012 (PDF) has more information on which the types of treatment devices available for many of the contaminants listed above.

Related topics

Our chemical page has information on the other substances that we can be exposed in drinking water, air, and soil.

We also have information on steps to take if your private wells has been impacted by a manure spill or by flooding.

DNR has a list of certified professionals that can help inspect wells and address issues.

DNR's well compensation grant program page has information about grants to address contamination in private for eligible landowners, renters and business owners.

The University of Wisconsin's How to Read Your Private Well Water Lab Report Guide (PDF) describes the different sections of a lab report, defines the terms used, and provides a step-by-step guide on how to determine if the results indicate a public health issue.


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Last revised November 14, 2023